This invention relates to a cushioning conversion machine and method and more particularly to improved stitching and/or coining means for such machines/methods.
In the process of shipping an item from one location to another, a protective packaging material is typically placed in the shipping case, or box, to fill any voids and/or to cushion the item during the shipping process. Some conventional protective packaging materials are plastic foam peanuts and plastic bubble pack. While these conventional plastic materials seem to adequately perform as cushioning products, they are not without disadvantages. Perhaps the most serious drawback of plastic bubble wrap and/or plastic foam peanuts is their effect on our environment. Quite simply, these plastic packaging materials are not biodegradable and thus they cannot avoid further multiplying our planet""s already critical waste disposal problems. The non-biodegradability of these packaging materials has become increasingly important in light of many industries adopting more progressive policies in terms of environmental responsibility.
These and other disadvantages of conventional plastic packaging materials have made paper protective packaging material a very popular alterative. Paper is biodegradable, recyclable and composed of a renewable resource, making it an environmentally responsible choice for conscientious industries.
While paper in sheet form could possibly be used as a protective packaging material, it is usually preferable to convert the sheets of paper into a relatively low density pad-like cushioning dunnage product. This conversion may be accomplished by a cushioning conversion machine/method, such as those disclosed in U.S. Pat. Nos. 3,509,798, 3,603,216, 3,655,500, 3,779,039, 4,026,198, 4,109,040, 4,717,613 and 4,750,896, and also in U.S. patent applications Ser. Nos. 07/533,755, 07/538,181, 07/592,572, 07/734,512, 07/786,573, 07/840,306 and 07/861,225. (These patents/applications are assigned to the assignee of the present invention and their entire disclosures are hereby incorporated by reference.)
In the conversion machines/methods disclosed in the above-identified patents and applications, the cushioning product is produced by converting multi-layer paper stock material into a desired geometry. The cushioning product includes pillow-like portions formed by the lateral edges of the stock paper being rolled inwardly to form a pair of twin spirals. The central regions of this structure are then compressed, connected, and/or coined to connect the overlapped edge portions thereby forming a cushioning product with a central compressed portion and two lateral pillow-like portions. This compression, connection and/or coining is performed by a pair of rotating members each include a plurality of radially outwardly extending projections (i.e., spur teeth) that meshingly engage.
To maintain the intactness of the cushioning product, the central portion of the cushioning product has also been xe2x80x9cstitchedxe2x80x9d to further prevent opening up or separation of the connected portions of the product, this commonly being referred to as xe2x80x9cunzipperingxe2x80x9d. For example, in U.S. Pat. No. 4,937,131 and/or U.S. Pat. No. 4,968,291, perforations are formed in the coined portion of the cushioning product by projection extending radially outward from the teeth of the rotating members. For another example, in U.S. patent application Ser. No. 08/607,607, tabs are formed in the coined portion by cutting edges that are radially positioned between the adjacent projections (spur teeth) on one of the rotating members and that circumferentially span the space between adjacent projections. (These patents and applications are assigned to the assignee of the present application and its entire disclosure is hereby incorporated by reference.)
Although the assemblies disclosed in the above-identified patents and applications adequately perform their coining, connecting and/or stitching functions, there is always room for more improvements, particularly improvements which allow these functions to be performed less power, less pinch pressure, and/or more control over the cushioning product""s density.
The present invention provides a cushioning conversion machine in which cutting edges used to form cutting tabs in the coined portion of the cushioning product have an abbreviated cutting edge. Particularly, the cutting edges do not span the circumferential extent of the valley (i.e., the space between adjacent teeth) in which they are located. The concentration of the tab-cutting force in a limited region reduces power requirements and/or allows the reduction of pinch pressure between the rotating members. Also, a concave edge profile may be provided on either side of the cutting edge to enhance the shearing ability of the cutting edge during its approach.
Additionally or alternatively, the present invention provides a cushioning conversion machine in which the coining members have projections shaped so that there is exaggerated backlash between meshing projections. Specifically, the present invention includes the appreciation that such an arrangement provides a more pronounced coining as may be advantageous in certain situations, such as when a higher density pad is desired. Moreover, these xe2x80x9cexaggerated backlashxe2x80x9d projections provide a direct, noticeable, and predictable relation between the pad density and the pinch pressure between the coining members thereby allowing the density of a cushioning product may be selectively changed by adjusting the pinch pressure.
The foregoing and other features of the invention are hereinafter fully described and particularly pointed out in the claims, the following description and annexed drawings setting forth in detail a certain illustrative embodiment of the invention, this embodiment being indicative, however, of but one of the various ways in which the principles of the invention may be employed.